Hi!
These are steps for Widows 2003 server in Windows 2008 server you will find the option add/remove program in Server Manager
a. Go to Control panel >> Add/Remove Programs >> Add/Remove Windows Components,Click on Accessories and utilities.
b. Click Next and you will get the screen choose Network services.
c. Choose the Networking Server (DO NOT CHECK THE BOX) and Click on Details and you will get screen Network services screen.
d. Check Box on DNS and Click OK >> then Next. It will start the installation and will popup for the CD.
e. Browse to the i386 folder and then Click OK to complete the installation of DNS Service and then click finish when the installation is done .